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Microbiology - Introduction > Microbial Mechanisms of Pathogenicity > Flashcards

Microbial Mechanisms of Pathogenicity Flashcards

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1
Q

Identify the principal portals of entry for pathogens

A
  1. Mucous membranes
  2. Skin
  3. The Parental Route
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2
Q

Name some bacteria that can induce host epithelial cells to engulf them

A
  1. E. coli
  2. Shigella
  3. Salmonella
  4. Neisseria gonorrhoeae
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3
Q

Contrast the nature and effects of exotoxins and endotoxins

A
  1. Exotoxins

2. Endotoxins:

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4
Q

What is the capacity of microorganisms to produce toxins called?

A

Toxigenicity

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5
Q

What is toxemia?

A

Toxemia refers to the presence of toxins in the blood

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6
Q

What is an Extoxin? Why is it harmful to the host?

A
  1. Exotoxin is a protein produced inside some bacteria as part of their growth and metabolism
  2. Exotoxin is secreted by the bacterium into the surrounding medium or released following lysis
  3. It acts like an enzyme, so even small amounts are quite harmful b/c they can be used over and over again
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7
Q

What is an antitoxin?

A

Antibodies to exotoxins

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8
Q

What is a toxoid?

A

Altered exotoxins are called toxoids
– Exotoxins are inactivated by heat or by formaldehyde, iodine or other chemicals, so they no longer cause the disease, but can still stimulate the body to produce antitoxins.

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9
Q

What are the 3 principal types of Exotoxins?

A
  1. A-B toxins
  2. Mem-disrupting toxins
  3. Superantigens
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10
Q

What is an A-B toxin?

A
  1. A-B toxin is also called type III toxin

2. It contains A part: the active (enzyme) component and B part: the binding component.

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11
Q

Give an example of A-B toxin and the mechanism of action in the host cell

A
  1. Diphtheria toxin is an example of A-B toxin
  2. Mechanism:
    a. Bacterium produces and releases exotoxin
    b. B part (binding component) binds to a host cell receptor and exotoxin enter the cell cytoplasm
    c. A part (active component) alters cell function by inhibiting protein synthesis
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12
Q

What is a mem.-disrupting toxin?

A
  1. Mem.-disrupting toxin is also called type II toxin
  2. Mem-disrupting toxin can either:
    a. Form protein channels in the plasma mem.
    b. Disrupt the phospholipid portion of the mem.
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13
Q

Give an example of bacterium that produce mem.-disrupting toxin

A

Clostridium perfringens

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14
Q

What is a leukocidin? How does it act?

A
  1. Mem.-disrupting toxin that kill phagocytic leukocytes (WBCs), ex. macrophages
  2. It act by forming protein channels.
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15
Q

Name two mem.-disrupting toxins and what bacteria produce them

A
  1. Leukocidins and Hemolysins
  2. Leukocidins: staphylococci, streptococci, and pneumococci.
  3. Hymolysins: staphylococci, streptococci
    a. Streptocci: Streptolysin can lyse both WBCs and RBCs
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16
Q

What is a hemolysin?

A

Hemolysin is a mem.-disrupting toxin that destroy erythrocytes (RBCs)

17
Q

What is a superantigen?

A
  1. Superantigen: type I toxin

2. An antigen that provoke a very intense immune response

18
Q

What is an endotoxin?

A
  1. Endotoxins are part of the outer portion of the cell wall of Gram (-) bacteria.
  2. Endotoxin is the lipid A of the LPS of Gram (-) bacteria.
19
Q

Match the following:

a. Endotoxin - LPS
b. Exotoxin - LPS
c. Endotoxin - protein
d. Exotoxin - protein

A

A & D

20
Q

How do endotoxins exert their effects on macrophages?

A

By stimulating macrophages to release cytokines in very high conc., at which level the cytokines are toxic.

21
Q

What symptoms do endotoxins cause?

A
  1. ALL endotoxins produce the same signs and symptoms, regardless of the species of microorganism:
    - - chills, fever, weakness, generalized aches, and shock and death in some cases.
  2. Endotoxins also activate blood-clotting proteins, causing the formation of small blood clots – obstructing capillaries and the resulting decreased blood supply induces the death of tissues.
22
Q

How does Endotoxin induce a fever?

A
  1. Gram (-) bacteria ingested by phagocytes and degraded in vacuoles.
  2. LPS of the bacterial cell wall are released (lipid A - endotoxin)
  3. Endotoxin cause macrophages to produce IL-1, which is carried to the hypothalamus (temp. control center)
  4. IL-1 induces the hypothalamus to release lipids called prostaglandins, resetting the thermostat in the hypothalamus at a higher temp.
23
Q

What is a septic shock?

Which gram bacteria causes endotoxic shock?

A
  1. Shock refers to any life-threatening loss of blood pressure.
  2. Shock caused by bacteria is called septic shock
  3. Gram (-) bacteria
24
Q

What is septic shock?

Which gram bacteria causes endotoxic shock?

A
  1. Shock refers to any life-threatening loss of blood pressure.
  2. Shock caused by bacteria is called septic shock
  3. Gram (-) bacteria
25
Q

What is the mechanism of septic shock?

A
  1. Gram (-) bacteria are phagocytized by macrophages
  2. Phagocytosis causes secretion of tumor necrosis factor (TNF), or cachectin.
  3. TNF binds to many tissues in the body and alters their metabolism:
    a. Damage blood capillaries – permeability is increased, and thus losing large amt. of fluid
  4. Low blood pressure results in shock.
26
Q

What is contact inhibition?

A

Contact inhibition: most normal cells cease growing in vitro when they come close to another cell

27
Q

How do viruses inhibit contact inhibition?

A

Viruses are capable of causing cancer transform host cells, which are abnormal, spindle-shaped cell that does not recognize contact inhibition.

28
Q

Which of the following is not a portal of entry for pathogens?

a. Mucous mem. of the respiratory tract
b. Mucous mem. of the GI tract
c. Skin
d. Blood
e. Parenteral route

A

D

Microbiology - Introduction (33 decks)

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